/*
** $Id: lparser.c,v 2.155 2016/08/01 19:51:24 roberto Exp $
** Lua Parser
** See Copyright Notice in lua.h
*/

#define lparser_c
#define LUA_CORE

#include "lprefix.h"


#include <string.h>

#include "lua.h"

#include "lcode.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "llex.h"
#include "lmem.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lparser.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"



/* maximum number of local variables per function (must be smaller
   than 250, due to the bytecode format) */
#define MAXVARS     200


#define hasmultret(k)       ((k) == VCALL || (k) == VVARARG)


/* because all strings are unified by the scanner, the parser
   can use pointer equality for string equality */
#define eqstr(a,b)  ((a) == (b))


/*
** nodes for block list (list of active blocks)
*/
typedef struct BlockCnt
{
    struct BlockCnt *previous;  /* chain */
    int firstlabel;  /* index of first label in this block */
    int firstgoto;  /* index of first pending goto in this block */
    lu_byte nactvar;  /* # active locals outside the block */
    lu_byte upval;  /* true if some variable in the block is an upvalue */
    lu_byte isloop;  /* true if 'block' is a loop */
} BlockCnt;



/*
** prototypes for recursive non-terminal functions
*/
static void statement(LexState *ls);
static void expr(LexState *ls, expdesc *v);


/* semantic error */
static l_noret semerror(LexState *ls, const char *msg)
{
    ls->t.token = 0;  /* remove "near <token>" from final message */
    luaX_syntaxerror(ls, msg);
}


static l_noret error_expected(LexState *ls, int token)
{
    luaX_syntaxerror(ls,
                     luaO_pushfstring(ls->L, "%s expected", luaX_token2str(ls, token)));
}


static l_noret errorlimit(FuncState *fs, int limit, const char *what)
{
    lua_State *L = fs->ls->L;
    const char *msg;
    int line = fs->f->linedefined;
    const char *where = (line == 0)
                        ? "main function"
                        : luaO_pushfstring(L, "function at line %d", line);
    msg = luaO_pushfstring(L, "too many %s (limit is %d) in %s",
                           what, limit, where);
    luaX_syntaxerror(fs->ls, msg);
}


static void checklimit(FuncState *fs, int v, int l, const char *what)
{
    if (v > l) errorlimit(fs, l, what);
}


static int testnext(LexState *ls, int c)
{
    if (ls->t.token == c)
    {
        luaX_next(ls);
        return 1;
    }
    else return 0;
}


static void check(LexState *ls, int c)
{
    if (ls->t.token != c)
        error_expected(ls, c);
}


static void checknext(LexState *ls, int c)
{
    check(ls, c);
    luaX_next(ls);
}


#define check_condition(ls,c,msg)   { if (!(c)) luaX_syntaxerror(ls, msg); }



static void check_match(LexState *ls, int what, int who, int where)
{
    if (!testnext(ls, what))
    {
        if (where == ls->linenumber)
            error_expected(ls, what);
        else
        {
            luaX_syntaxerror(ls, luaO_pushfstring(ls->L,
                                                  "%s expected (to close %s at line %d)",
                                                  luaX_token2str(ls, what), luaX_token2str(ls, who), where));
        }
    }
}


static TString *str_checkname(LexState *ls)
{
    TString *ts;
    check(ls, TK_NAME);
    ts = ls->t.seminfo.ts;
    luaX_next(ls);
    return ts;
}


static void init_exp(expdesc *e, expkind k, int i)
{
    e->f = e->t = NO_JUMP;
    e->k = k;
    e->u.info = i;
}


static void codestring(LexState *ls, expdesc *e, TString *s)
{
    init_exp(e, VK, luaK_stringK(ls->fs, s));
}


static void checkname(LexState *ls, expdesc *e)
{
    codestring(ls, e, str_checkname(ls));
}


static int registerlocalvar(LexState *ls, TString *varname)
{
    FuncState *fs = ls->fs;
    Proto *f = fs->f;
    int oldsize = f->sizelocvars;
    luaM_growvector(ls->L, f->locvars, fs->nlocvars, f->sizelocvars,
                    LocVar, SHRT_MAX, "local variables");
    while (oldsize < f->sizelocvars)
        f->locvars[oldsize++].varname = NULL;
    f->locvars[fs->nlocvars].varname = varname;
    luaC_objbarrier(ls->L, f, varname);
    return fs->nlocvars++;
}


static void new_localvar(LexState *ls, TString *name)
{
    FuncState *fs = ls->fs;
    Dyndata *dyd = ls->dyd;
    int reg = registerlocalvar(ls, name);
    checklimit(fs, dyd->actvar.n + 1 - fs->firstlocal,
               MAXVARS, "local variables");
    luaM_growvector(ls->L, dyd->actvar.arr, dyd->actvar.n + 1,
                    dyd->actvar.size, Vardesc, MAX_INT, "local variables");
    dyd->actvar.arr[dyd->actvar.n++].idx = cast(short, reg);
}


static void new_localvarliteral_(LexState *ls, const char *name, size_t sz)
{
    new_localvar(ls, luaX_newstring(ls, name, sz));
}

#define new_localvarliteral(ls,v) \
    new_localvarliteral_(ls, "" v, (sizeof(v)/sizeof(char))-1)


static LocVar *getlocvar(FuncState *fs, int i)
{
    int idx = fs->ls->dyd->actvar.arr[fs->firstlocal + i].idx;
    lua_assert(idx < fs->nlocvars);
    return &fs->f->locvars[idx];
}


static void adjustlocalvars(LexState *ls, int nvars)
{
    FuncState *fs = ls->fs;
    fs->nactvar = cast_byte(fs->nactvar + nvars);
    for (; nvars; nvars--)
    {
        getlocvar(fs, fs->nactvar - nvars)->startpc = fs->pc;
    }
}


static void removevars(FuncState *fs, int tolevel)
{
    fs->ls->dyd->actvar.n -= (fs->nactvar - tolevel);
    while (fs->nactvar > tolevel)
        getlocvar(fs, --fs->nactvar)->endpc = fs->pc;
}


static int searchupvalue(FuncState *fs, TString *name)
{
    int i;
    Upvaldesc *up = fs->f->upvalues;
    for (i = 0; i < fs->nups; i++)
    {
        if (eqstr(up[i].name, name)) return i;
    }
    return -1;  /* not found */
}


static int newupvalue(FuncState *fs, TString *name, expdesc *v)
{
    Proto *f = fs->f;
    int oldsize = f->sizeupvalues;
    checklimit(fs, fs->nups + 1, MAXUPVAL, "upvalues");
    luaM_growvector(fs->ls->L, f->upvalues, fs->nups, f->sizeupvalues,
                    Upvaldesc, MAXUPVAL, "upvalues");
    while (oldsize < f->sizeupvalues)
        f->upvalues[oldsize++].name = NULL;
    f->upvalues[fs->nups].instack = (v->k == VLOCAL);
    f->upvalues[fs->nups].idx = cast_byte(v->u.info);
    f->upvalues[fs->nups].name = name;
    luaC_objbarrier(fs->ls->L, f, name);
    return fs->nups++;
}


static int searchvar(FuncState *fs, TString *n)
{
    int i;
    for (i = cast_int(fs->nactvar) - 1; i >= 0; i--)
    {
        if (eqstr(n, getlocvar(fs, i)->varname))
            return i;
    }
    return -1;  /* not found */
}


/*
  Mark block where variable at given level was defined
  (to emit close instructions later).
*/
static void markupval(FuncState *fs, int level)
{
    BlockCnt *bl = fs->bl;
    while (bl->nactvar > level)
        bl = bl->previous;
    bl->upval = 1;
}


/*
  Find variable with given name 'n'. If it is an upvalue, add this
  upvalue into all intermediate functions.
*/
static void singlevaraux(FuncState *fs, TString *n, expdesc *var, int base)
{
    if (fs == NULL)  /* no more levels? */
        init_exp(var, VVOID, 0);  /* default is global */
    else
    {
        int v = searchvar(fs, n);  /* look up locals at current level */
        if (v >= 0)    /* found? */
        {
            init_exp(var, VLOCAL, v);  /* variable is local */
            if (!base)
                markupval(fs, v);  /* local will be used as an upval */
        }
        else    /* not found as local at current level; try upvalues */
        {
            int idx = searchupvalue(fs, n);  /* try existing upvalues */
            if (idx < 0)    /* not found? */
            {
                singlevaraux(fs->prev, n, var, 0);  /* try upper levels */
                if (var->k == VVOID)  /* not found? */
                    return;  /* it is a global */
                /* else was LOCAL or UPVAL */
                idx  = newupvalue(fs, n, var);  /* will be a new upvalue */
            }
            init_exp(var, VUPVAL, idx);  /* new or old upvalue */
        }
    }
}


static void singlevar(LexState *ls, expdesc *var)
{
    TString *varname = str_checkname(ls);
    FuncState *fs = ls->fs;
    singlevaraux(fs, varname, var, 1);
    if (var->k == VVOID)    /* global name? */
    {
        expdesc key;
        singlevaraux(fs, ls->envn, var, 1);  /* get environment variable */
        lua_assert(var->k != VVOID);  /* this one must exist */
        codestring(ls, &key, varname);  /* key is variable name */
        luaK_indexed(fs, var, &key);  /* env[varname] */
    }
}


static void adjust_assign(LexState *ls, int nvars, int nexps, expdesc *e)
{
    FuncState *fs = ls->fs;
    int extra = nvars - nexps;
    if (hasmultret(e->k))
    {
        extra++;  /* includes call itself */
        if (extra < 0) extra = 0;
        luaK_setreturns(fs, e, extra);  /* last exp. provides the difference */
        if (extra > 1) luaK_reserveregs(fs, extra - 1);
    }
    else
    {
        if (e->k != VVOID) luaK_exp2nextreg(fs, e);  /* close last expression */
        if (extra > 0)
        {
            int reg = fs->freereg;
            luaK_reserveregs(fs, extra);
            luaK_nil(fs, reg, extra);
        }
    }
    if (nexps > nvars)
        ls->fs->freereg -= nexps - nvars;  /* remove extra values */
}


static void enterlevel(LexState *ls)
{
    lua_State *L = ls->L;
    ++L->nCcalls;
    checklimit(ls->fs, L->nCcalls, LUAI_MAXCCALLS, "C levels");
}


#define leavelevel(ls)  ((ls)->L->nCcalls--)


static void closegoto(LexState *ls, int g, Labeldesc *label)
{
    int i;
    FuncState *fs = ls->fs;
    Labellist *gl = &ls->dyd->gt;
    Labeldesc *gt = &gl->arr[g];
    lua_assert(eqstr(gt->name, label->name));
    if (gt->nactvar < label->nactvar)
    {
        TString *vname = getlocvar(fs, gt->nactvar)->varname;
        const char *msg = luaO_pushfstring(ls->L,
                                           "<goto %s> at line %d jumps into the scope of local '%s'",
                                           getstr(gt->name), gt->line, getstr(vname));
        semerror(ls, msg);
    }
    luaK_patchlist(fs, gt->pc, label->pc);
    /* remove goto from pending list */
    for (i = g; i < gl->n - 1; i++)
        gl->arr[i] = gl->arr[i + 1];
    gl->n--;
}


/*
** try to close a goto with existing labels; this solves backward jumps
*/
static int findlabel(LexState *ls, int g)
{
    int i;
    BlockCnt *bl = ls->fs->bl;
    Dyndata *dyd = ls->dyd;
    Labeldesc *gt = &dyd->gt.arr[g];
    /* check labels in current block for a match */
    for (i = bl->firstlabel; i < dyd->label.n; i++)
    {
        Labeldesc *lb = &dyd->label.arr[i];
        if (eqstr(lb->name, gt->name))    /* correct label? */
        {
            if (gt->nactvar > lb->nactvar &&
                    (bl->upval || dyd->label.n > bl->firstlabel))
                luaK_patchclose(ls->fs, gt->pc, lb->nactvar);
            closegoto(ls, g, lb);  /* close it */
            return 1;
        }
    }
    return 0;  /* label not found; cannot close goto */
}


static int newlabelentry(LexState *ls, Labellist *l, TString *name,
                         int line, int pc)
{
    int n = l->n;
    luaM_growvector(ls->L, l->arr, n, l->size,
                    Labeldesc, SHRT_MAX, "labels/gotos");
    l->arr[n].name = name;
    l->arr[n].line = line;
    l->arr[n].nactvar = ls->fs->nactvar;
    l->arr[n].pc = pc;
    l->n = n + 1;
    return n;
}


/*
** check whether new label 'lb' matches any pending gotos in current
** block; solves forward jumps
*/
static void findgotos(LexState *ls, Labeldesc *lb)
{
    Labellist *gl = &ls->dyd->gt;
    int i = ls->fs->bl->firstgoto;
    while (i < gl->n)
    {
        if (eqstr(gl->arr[i].name, lb->name))
            closegoto(ls, i, lb);
        else
            i++;
    }
}


/*
** export pending gotos to outer level, to check them against
** outer labels; if the block being exited has upvalues, and
** the goto exits the scope of any variable (which can be the
** upvalue), close those variables being exited.
*/
static void movegotosout(FuncState *fs, BlockCnt *bl)
{
    int i = bl->firstgoto;
    Labellist *gl = &fs->ls->dyd->gt;
    /* correct pending gotos to current block and try to close it
       with visible labels */
    while (i < gl->n)
    {
        Labeldesc *gt = &gl->arr[i];
        if (gt->nactvar > bl->nactvar)
        {
            if (bl->upval)
                luaK_patchclose(fs, gt->pc, bl->nactvar);
            gt->nactvar = bl->nactvar;
        }
        if (!findlabel(fs->ls, i))
            i++;  /* move to next one */
    }
}


static void enterblock(FuncState *fs, BlockCnt *bl, lu_byte isloop)
{
    bl->isloop = isloop;
    bl->nactvar = fs->nactvar;
    bl->firstlabel = fs->ls->dyd->label.n;
    bl->firstgoto = fs->ls->dyd->gt.n;
    bl->upval = 0;
    bl->previous = fs->bl;
    fs->bl = bl;
    lua_assert(fs->freereg == fs->nactvar);
}


/*
** create a label named 'break' to resolve break statements
*/
static void breaklabel(LexState *ls)
{
    TString *n = luaS_new(ls->L, "break");
    int l = newlabelentry(ls, &ls->dyd->label, n, 0, ls->fs->pc);
    findgotos(ls, &ls->dyd->label.arr[l]);
}

/*
** generates an error for an undefined 'goto'; choose appropriate
** message when label name is a reserved word (which can only be 'break')
*/
static l_noret undefgoto(LexState *ls, Labeldesc *gt)
{
    const char *msg = isreserved(gt->name)
                      ? "<%s> at line %d not inside a loop"
                      : "no visible label '%s' for <goto> at line %d";
    msg = luaO_pushfstring(ls->L, msg, getstr(gt->name), gt->line);
    semerror(ls, msg);
}


static void leaveblock(FuncState *fs)
{
    BlockCnt *bl = fs->bl;
    LexState *ls = fs->ls;
    if (bl->previous && bl->upval)
    {
        /* create a 'jump to here' to close upvalues */
        int j = luaK_jump(fs);
        luaK_patchclose(fs, j, bl->nactvar);
        luaK_patchtohere(fs, j);
    }
    if (bl->isloop)
        breaklabel(ls);  /* close pending breaks */
    fs->bl = bl->previous;
    removevars(fs, bl->nactvar);
    lua_assert(bl->nactvar == fs->nactvar);
    fs->freereg = fs->nactvar;  /* free registers */
    ls->dyd->label.n = bl->firstlabel;  /* remove local labels */
    if (bl->previous)  /* inner block? */
        movegotosout(fs, bl);  /* update pending gotos to outer block */
    else if (bl->firstgoto < ls->dyd->gt.n)  /* pending gotos in outer block? */
        undefgoto(ls, &ls->dyd->gt.arr[bl->firstgoto]);  /* error */
}


/*
** adds a new prototype into list of prototypes
*/
static Proto *addprototype(LexState *ls)
{
    Proto *clp;
    lua_State *L = ls->L;
    FuncState *fs = ls->fs;
    Proto *f = fs->f;  /* prototype of current function */
    if (fs->np >= f->sizep)
    {
        int oldsize = f->sizep;
        luaM_growvector(L, f->p, fs->np, f->sizep, Proto *, MAXARG_Bx, "functions");
        while (oldsize < f->sizep)
            f->p[oldsize++] = NULL;
    }
    f->p[fs->np++] = clp = luaF_newproto(L);
    luaC_objbarrier(L, f, clp);
    return clp;
}


/*
** codes instruction to create new closure in parent function.
** The OP_CLOSURE instruction must use the last available register,
** so that, if it invokes the GC, the GC knows which registers
** are in use at that time.
*/
static void codeclosure(LexState *ls, expdesc *v)
{
    FuncState *fs = ls->fs->prev;
    init_exp(v, VRELOCABLE, luaK_codeABx(fs, OP_CLOSURE, 0, fs->np - 1));
    luaK_exp2nextreg(fs, v);  /* fix it at the last register */
}


static void open_func(LexState *ls, FuncState *fs, BlockCnt *bl)
{
    Proto *f;
    fs->prev = ls->fs;  /* linked list of funcstates */
    fs->ls = ls;
    ls->fs = fs;
    fs->pc = 0;
    fs->lasttarget = 0;
    fs->jpc = NO_JUMP;
    fs->freereg = 0;
    fs->nk = 0;
    fs->np = 0;
    fs->nups = 0;
    fs->nlocvars = 0;
    fs->nactvar = 0;
    fs->firstlocal = ls->dyd->actvar.n;
    fs->bl = NULL;
    f = fs->f;
    f->source = ls->source;
    f->maxstacksize = 2;  /* registers 0/1 are always valid */
    enterblock(fs, bl, 0);
}


static void close_func(LexState *ls)
{
    lua_State *L = ls->L;
    FuncState *fs = ls->fs;
    Proto *f = fs->f;
    luaK_ret(fs, 0, 0);  /* final return */
    leaveblock(fs);
    luaM_reallocvector(L, f->code, f->sizecode, fs->pc, Instruction);
    f->sizecode = fs->pc;
    luaM_reallocvector(L, f->lineinfo, f->sizelineinfo, fs->pc, int);
    f->sizelineinfo = fs->pc;
    luaM_reallocvector(L, f->k, f->sizek, fs->nk, TValue);
    f->sizek = fs->nk;
    luaM_reallocvector(L, f->p, f->sizep, fs->np, Proto *);
    f->sizep = fs->np;
    luaM_reallocvector(L, f->locvars, f->sizelocvars, fs->nlocvars, LocVar);
    f->sizelocvars = fs->nlocvars;
    luaM_reallocvector(L, f->upvalues, f->sizeupvalues, fs->nups, Upvaldesc);
    f->sizeupvalues = fs->nups;
    lua_assert(fs->bl == NULL);
    ls->fs = fs->prev;
    luaC_checkGC(L);
}



/*============================================================*/
/* GRAMMAR RULES */
/*============================================================*/


/*
** check whether current token is in the follow set of a block.
** 'until' closes syntactical blocks, but do not close scope,
** so it is handled in separate.
*/
static int block_follow(LexState *ls, int withuntil)
{
    switch (ls->t.token)
    {
    case TK_ELSE:
    case TK_ELSEIF:
    case TK_END:
    case TK_EOS:
        return 1;
    case TK_UNTIL:
        return withuntil;
    default:
        return 0;
    }
}


static void statlist(LexState *ls)
{
    /* statlist -> { stat [';'] } */
    while (!block_follow(ls, 1))
    {
        if (ls->t.token == TK_RETURN)
        {
            statement(ls);
            return;  /* 'return' must be last statement */
        }
        statement(ls);
    }
}


static void fieldsel(LexState *ls, expdesc *v)
{
    /* fieldsel -> ['.' | ':'] NAME */
    FuncState *fs = ls->fs;
    expdesc key;
    luaK_exp2anyregup(fs, v);
    luaX_next(ls);  /* skip the dot or colon */
    checkname(ls, &key);
    luaK_indexed(fs, v, &key);
}


static void yindex(LexState *ls, expdesc *v)
{
    /* index -> '[' expr ']' */
    luaX_next(ls);  /* skip the '[' */
    expr(ls, v);
    luaK_exp2val(ls->fs, v);
    checknext(ls, ']');
}


/*
** {======================================================================
** Rules for Constructors
** =======================================================================
*/


struct ConsControl
{
    expdesc v;  /* last list item read */
    expdesc *t;  /* table descriptor */
    int nh;  /* total number of 'record' elements */
    int na;  /* total number of array elements */
    int tostore;  /* number of array elements pending to be stored */
};


static void recfield(LexState *ls, struct ConsControl *cc)
{
    /* recfield -> (NAME | '['exp1']') = exp1 */
    FuncState *fs = ls->fs;
    int reg = ls->fs->freereg;
    expdesc key, val;
    int rkkey;
    if (ls->t.token == TK_NAME)
    {
        checklimit(fs, cc->nh, MAX_INT, "items in a constructor");
        checkname(ls, &key);
    }
    else  /* ls->t.token == '[' */
        yindex(ls, &key);
    cc->nh++;
    checknext(ls, '=');
    rkkey = luaK_exp2RK(fs, &key);
    expr(ls, &val);
    luaK_codeABC(fs, OP_SETTABLE, cc->t->u.info, rkkey, luaK_exp2RK(fs, &val));
    fs->freereg = reg;  /* free registers */
}


static void closelistfield(FuncState *fs, struct ConsControl *cc)
{
    if (cc->v.k == VVOID) return;  /* there is no list item */
    luaK_exp2nextreg(fs, &cc->v);
    cc->v.k = VVOID;
    if (cc->tostore == LFIELDS_PER_FLUSH)
    {
        luaK_setlist(fs, cc->t->u.info, cc->na, cc->tostore);  /* flush */
        cc->tostore = 0;  /* no more items pending */
    }
}


static void lastlistfield(FuncState *fs, struct ConsControl *cc)
{
    if (cc->tostore == 0) return;
    if (hasmultret(cc->v.k))
    {
        luaK_setmultret(fs, &cc->v);
        luaK_setlist(fs, cc->t->u.info, cc->na, LUA_MULTRET);
        cc->na--;  /* do not count last expression (unknown number of elements) */
    }
    else
    {
        if (cc->v.k != VVOID)
            luaK_exp2nextreg(fs, &cc->v);
        luaK_setlist(fs, cc->t->u.info, cc->na, cc->tostore);
    }
}


static void listfield(LexState *ls, struct ConsControl *cc)
{
    /* listfield -> exp */
    expr(ls, &cc->v);
    checklimit(ls->fs, cc->na, MAX_INT, "items in a constructor");
    cc->na++;
    cc->tostore++;
}


static void field(LexState *ls, struct ConsControl *cc)
{
    /* field -> listfield | recfield */
    switch (ls->t.token)
    {
    case TK_NAME:    /* may be 'listfield' or 'recfield' */
    {
        if (luaX_lookahead(ls) != '=')  /* expression? */
            listfield(ls, cc);
        else
            recfield(ls, cc);
        break;
    }
    case '[':
    {
        recfield(ls, cc);
        break;
    }
    default:
    {
        listfield(ls, cc);
        break;
    }
    }
}


static void constructor(LexState *ls, expdesc *t)
{
    /* constructor -> '{' [ field { sep field } [sep] ] '}'
       sep -> ',' | ';' */
    FuncState *fs = ls->fs;
    int line = ls->linenumber;
    int pc = luaK_codeABC(fs, OP_NEWTABLE, 0, 0, 0);
    struct ConsControl cc;
    cc.na = cc.nh = cc.tostore = 0;
    cc.t = t;
    init_exp(t, VRELOCABLE, pc);
    init_exp(&cc.v, VVOID, 0);  /* no value (yet) */
    luaK_exp2nextreg(ls->fs, t);  /* fix it at stack top */
    checknext(ls, '{');
    do
    {
        lua_assert(cc.v.k == VVOID || cc.tostore > 0);
        if (ls->t.token == '}') break;
        closelistfield(fs, &cc);
        field(ls, &cc);
    }
    while (testnext(ls, ',') || testnext(ls, ';'));
    check_match(ls, '}', '{', line);
    lastlistfield(fs, &cc);
    SETARG_B(fs->f->code[pc], luaO_int2fb(cc.na)); /* set initial array size */
    SETARG_C(fs->f->code[pc], luaO_int2fb(cc.nh));  /* set initial table size */
}

/* }====================================================================== */



static void parlist(LexState *ls)
{
    /* parlist -> [ param { ',' param } ] */
    FuncState *fs = ls->fs;
    Proto *f = fs->f;
    int nparams = 0;
    f->is_vararg = 0;
    if (ls->t.token != ')')    /* is 'parlist' not empty? */
    {
        do
        {
            switch (ls->t.token)
            {
            case TK_NAME:    /* param -> NAME */
            {
                new_localvar(ls, str_checkname(ls));
                nparams++;
                break;
            }
            case TK_DOTS:    /* param -> '...' */
            {
                luaX_next(ls);
                f->is_vararg = 1;  /* declared vararg */
                break;
            }
            default:
                luaX_syntaxerror(ls, "<name> or '...' expected");
            }
        }
        while (!f->is_vararg && testnext(ls, ','));
    }
    adjustlocalvars(ls, nparams);
    f->numparams = cast_byte(fs->nactvar);
    luaK_reserveregs(fs, fs->nactvar);  /* reserve register for parameters */
}


static void body(LexState *ls, expdesc *e, int ismethod, int line)
{
    /* body ->  '(' parlist ')' block END */
    FuncState new_fs;
    BlockCnt bl;
    new_fs.f = addprototype(ls);
    new_fs.f->linedefined = line;
    open_func(ls, &new_fs, &bl);
    checknext(ls, '(');
    if (ismethod)
    {
        new_localvarliteral(ls, "self");  /* create 'self' parameter */
        adjustlocalvars(ls, 1);
    }
    parlist(ls);
    checknext(ls, ')');
    statlist(ls);
    new_fs.f->lastlinedefined = ls->linenumber;
    check_match(ls, TK_END, TK_FUNCTION, line);
    codeclosure(ls, e);
    close_func(ls);
}


static int explist(LexState *ls, expdesc *v)
{
    /* explist -> expr { ',' expr } */
    int n = 1;  /* at least one expression */
    expr(ls, v);
    while (testnext(ls, ','))
    {
        luaK_exp2nextreg(ls->fs, v);
        expr(ls, v);
        n++;
    }
    return n;
}


static void funcargs(LexState *ls, expdesc *f, int line)
{
    FuncState *fs = ls->fs;
    expdesc args;
    int base, nparams;
    switch (ls->t.token)
    {
    case '(':    /* funcargs -> '(' [ explist ] ')' */
    {
        luaX_next(ls);
        if (ls->t.token == ')')  /* arg list is empty? */
            args.k = VVOID;
        else
        {
            explist(ls, &args);
            luaK_setmultret(fs, &args);
        }
        check_match(ls, ')', '(', line);
        break;
    }
    case '{':    /* funcargs -> constructor */
    {
        constructor(ls, &args);
        break;
    }
    case TK_STRING:    /* funcargs -> STRING */
    {
        codestring(ls, &args, ls->t.seminfo.ts);
        luaX_next(ls);  /* must use 'seminfo' before 'next' */
        break;
    }
    default:
    {
        luaX_syntaxerror(ls, "function arguments expected");
    }
    }
    lua_assert(f->k == VNONRELOC);
    base = f->u.info;  /* base register for call */
    if (hasmultret(args.k))
        nparams = LUA_MULTRET;  /* open call */
    else
    {
        if (args.k != VVOID)
            luaK_exp2nextreg(fs, &args);  /* close last argument */
        nparams = fs->freereg - (base + 1);
    }
    init_exp(f, VCALL, luaK_codeABC(fs, OP_CALL, base, nparams + 1, 2));
    luaK_fixline(fs, line);
    fs->freereg = base + 1;  /* call remove function and arguments and leaves
                            (unless changed) one result */
}




/*
** {======================================================================
** Expression parsing
** =======================================================================
*/


static void primaryexp(LexState *ls, expdesc *v)
{
    /* primaryexp -> NAME | '(' expr ')' */
    switch (ls->t.token)
    {
    case '(':
    {
        int line = ls->linenumber;
        luaX_next(ls);
        expr(ls, v);
        check_match(ls, ')', '(', line);
        luaK_dischargevars(ls->fs, v);
        return;
    }
    case TK_NAME:
    {
        singlevar(ls, v);
        return;
    }
    default:
    {
        luaX_syntaxerror(ls, "unexpected symbol");
    }
    }
}


static void suffixedexp(LexState *ls, expdesc *v)
{
    /* suffixedexp ->
         primaryexp { '.' NAME | '[' exp ']' | ':' NAME funcargs | funcargs } */
    FuncState *fs = ls->fs;
    int line = ls->linenumber;
    primaryexp(ls, v);
    for (;;)
    {
        switch (ls->t.token)
        {
        case '.':    /* fieldsel */
        {
            fieldsel(ls, v);
            break;
        }
        case '[':    /* '[' exp1 ']' */
        {
            expdesc key;
            luaK_exp2anyregup(fs, v);
            yindex(ls, &key);
            luaK_indexed(fs, v, &key);
            break;
        }
        case ':':    /* ':' NAME funcargs */
        {
            expdesc key;
            luaX_next(ls);
            checkname(ls, &key);
            luaK_self(fs, v, &key);
            funcargs(ls, v, line);
            break;
        }
        case '(':
        case TK_STRING:
        case '{':    /* funcargs */
        {
            luaK_exp2nextreg(fs, v);
            funcargs(ls, v, line);
            break;
        }
        default:
            return;
        }
    }
}


static void simpleexp(LexState *ls, expdesc *v)
{
    /* simpleexp -> FLT | INT | STRING | NIL | TRUE | FALSE | ... |
                    constructor | FUNCTION body | suffixedexp */
    switch (ls->t.token)
    {
    case TK_FLT:
    {
        init_exp(v, VKFLT, 0);
        v->u.nval = ls->t.seminfo.r;
        break;
    }
    case TK_INT:
    {
        init_exp(v, VKINT, 0);
        v->u.ival = ls->t.seminfo.i;
        break;
    }
    case TK_STRING:
    {
        codestring(ls, v, ls->t.seminfo.ts);
        break;
    }
    case TK_NIL:
    {
        init_exp(v, VNIL, 0);
        break;
    }
    case TK_TRUE:
    {
        init_exp(v, VTRUE, 0);
        break;
    }
    case TK_FALSE:
    {
        init_exp(v, VFALSE, 0);
        break;
    }
    case TK_DOTS:    /* vararg */
    {
        FuncState *fs = ls->fs;
        check_condition(ls, fs->f->is_vararg,
                        "cannot use '...' outside a vararg function");
        init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 1, 0));
        break;
    }
    case '{':    /* constructor */
    {
        constructor(ls, v);
        return;
    }
    case TK_FUNCTION:
    {
        luaX_next(ls);
        body(ls, v, 0, ls->linenumber);
        return;
    }
    default:
    {
        suffixedexp(ls, v);
        return;
    }
    }
    luaX_next(ls);
}


static UnOpr getunopr(int op)
{
    switch (op)
    {
    case TK_NOT:
        return OPR_NOT;
    case '-':
        return OPR_MINUS;
    case '~':
        return OPR_BNOT;
    case '#':
        return OPR_LEN;
    default:
        return OPR_NOUNOPR;
    }
}


static BinOpr getbinopr(int op)
{
    switch (op)
    {
    case '+':
        return OPR_ADD;
    case '-':
        return OPR_SUB;
    case '*':
        return OPR_MUL;
    case '%':
        return OPR_MOD;
    case '^':
        return OPR_POW;
    case '/':
        return OPR_DIV;
    case TK_IDIV:
        return OPR_IDIV;
    case '&':
        return OPR_BAND;
    case '|':
        return OPR_BOR;
    case '~':
        return OPR_BXOR;
    case TK_SHL:
        return OPR_SHL;
    case TK_SHR:
        return OPR_SHR;
    case TK_CONCAT:
        return OPR_CONCAT;
    case TK_NE:
        return OPR_NE;
    case TK_EQ:
        return OPR_EQ;
    case '<':
        return OPR_LT;
    case TK_LE:
        return OPR_LE;
    case '>':
        return OPR_GT;
    case TK_GE:
        return OPR_GE;
    case TK_AND:
        return OPR_AND;
    case TK_OR:
        return OPR_OR;
    default:
        return OPR_NOBINOPR;
    }
}


static const struct
{
    lu_byte left;  /* left priority for each binary operator */
    lu_byte right; /* right priority */
} priority[] =    /* ORDER OPR */
{
    {10, 10}, {10, 10},           /* '+' '-' */
    {11, 11}, {11, 11},           /* '*' '%' */
    {14, 13},                  /* '^' (right associative) */
    {11, 11}, {11, 11},           /* '/' '//' */
    {6, 6}, {4, 4}, {5, 5},   /* '&' '|' '~' */
    {7, 7}, {7, 7},           /* '<<' '>>' */
    {9, 8},                   /* '..' (right associative) */
    {3, 3}, {3, 3}, {3, 3},   /* ==, <, <= */
    {3, 3}, {3, 3}, {3, 3},   /* ~=, >, >= */
    {2, 2}, {1, 1}            /* and, or */
};

#define UNARY_PRIORITY  12  /* priority for unary operators */


/*
** subexpr -> (simpleexp | unop subexpr) { binop subexpr }
** where 'binop' is any binary operator with a priority higher than 'limit'
*/
static BinOpr subexpr(LexState *ls, expdesc *v, int limit)
{
    BinOpr op;
    UnOpr uop;
    enterlevel(ls);
    uop = getunopr(ls->t.token);
    if (uop != OPR_NOUNOPR)
    {
        int line = ls->linenumber;
        luaX_next(ls);
        subexpr(ls, v, UNARY_PRIORITY);
        luaK_prefix(ls->fs, uop, v, line);
    }
    else simpleexp(ls, v);
    /* expand while operators have priorities higher than 'limit' */
    op = getbinopr(ls->t.token);
    while (op != OPR_NOBINOPR && priority[op].left > limit)
    {
        expdesc v2;
        BinOpr nextop;
        int line = ls->linenumber;
        luaX_next(ls);
        luaK_infix(ls->fs, op, v);
        /* read sub-expression with higher priority */
        nextop = subexpr(ls, &v2, priority[op].right);
        luaK_posfix(ls->fs, op, v, &v2, line);
        op = nextop;
    }
    leavelevel(ls);
    return op;  /* return first untreated operator */
}


static void expr(LexState *ls, expdesc *v)
{
    subexpr(ls, v, 0);
}

/* }==================================================================== */



/*
** {======================================================================
** Rules for Statements
** =======================================================================
*/


static void block(LexState *ls)
{
    /* block -> statlist */
    FuncState *fs = ls->fs;
    BlockCnt bl;
    enterblock(fs, &bl, 0);
    statlist(ls);
    leaveblock(fs);
}


/*
** structure to chain all variables in the left-hand side of an
** assignment
*/
struct LHS_assign
{
    struct LHS_assign *prev;
    expdesc v;  /* variable (global, local, upvalue, or indexed) */
};


/*
** check whether, in an assignment to an upvalue/local variable, the
** upvalue/local variable is begin used in a previous assignment to a
** table. If so, save original upvalue/local value in a safe place and
** use this safe copy in the previous assignment.
*/
static void check_conflict(LexState *ls, struct LHS_assign *lh, expdesc *v)
{
    FuncState *fs = ls->fs;
    int extra = fs->freereg;  /* eventual position to save local variable */
    int conflict = 0;
    for (; lh; lh = lh->prev)    /* check all previous assignments */
    {
        if (lh->v.k == VINDEXED)    /* assigning to a table? */
        {
            /* table is the upvalue/local being assigned now? */
            if (lh->v.u.ind.vt == v->k && lh->v.u.ind.t == v->u.info)
            {
                conflict = 1;
                lh->v.u.ind.vt = VLOCAL;
                lh->v.u.ind.t = extra;  /* previous assignment will use safe copy */
            }
            /* index is the local being assigned? (index cannot be upvalue) */
            if (v->k == VLOCAL && lh->v.u.ind.idx == v->u.info)
            {
                conflict = 1;
                lh->v.u.ind.idx = extra;  /* previous assignment will use safe copy */
            }
        }
    }
    if (conflict)
    {
        /* copy upvalue/local value to a temporary (in position 'extra') */
        OpCode op = (v->k == VLOCAL) ? OP_MOVE : OP_GETUPVAL;
        luaK_codeABC(fs, op, extra, v->u.info, 0);
        luaK_reserveregs(fs, 1);
    }
}


static void assignment(LexState *ls, struct LHS_assign *lh, int nvars)
{
    expdesc e;
    check_condition(ls, vkisvar(lh->v.k), "syntax error");
    if (testnext(ls, ','))    /* assignment -> ',' suffixedexp assignment */
    {
        struct LHS_assign nv;
        nv.prev = lh;
        suffixedexp(ls, &nv.v);
        if (nv.v.k != VINDEXED)
            check_conflict(ls, lh, &nv.v);
        checklimit(ls->fs, nvars + ls->L->nCcalls, LUAI_MAXCCALLS,
                   "C levels");
        assignment(ls, &nv, nvars + 1);
    }
    else    /* assignment -> '=' explist */
    {
        int nexps;
        checknext(ls, '=');
        nexps = explist(ls, &e);
        if (nexps != nvars)
            adjust_assign(ls, nvars, nexps, &e);
        else
        {
            luaK_setoneret(ls->fs, &e);  /* close last expression */
            luaK_storevar(ls->fs, &lh->v, &e);
            return;  /* avoid default */
        }
    }
    init_exp(&e, VNONRELOC, ls->fs->freereg - 1); /* default assignment */
    luaK_storevar(ls->fs, &lh->v, &e);
}


static int cond(LexState *ls)
{
    /* cond -> exp */
    expdesc v;
    expr(ls, &v);  /* read condition */
    if (v.k == VNIL) v.k = VFALSE;  /* 'falses' are all equal here */
    luaK_goiftrue(ls->fs, &v);
    return v.f;
}


static void gotostat(LexState *ls, int pc)
{
    int line = ls->linenumber;
    TString *label;
    int g;
    if (testnext(ls, TK_GOTO))
        label = str_checkname(ls);
    else
    {
        luaX_next(ls);  /* skip break */
        label = luaS_new(ls->L, "break");
    }
    g = newlabelentry(ls, &ls->dyd->gt, label, line, pc);
    findlabel(ls, g);  /* close it if label already defined */
}


/* check for repeated labels on the same block */
static void checkrepeated(FuncState *fs, Labellist *ll, TString *label)
{
    int i;
    for (i = fs->bl->firstlabel; i < ll->n; i++)
    {
        if (eqstr(label, ll->arr[i].name))
        {
            const char *msg = luaO_pushfstring(fs->ls->L,
                                               "label '%s' already defined on line %d",
                                               getstr(label), ll->arr[i].line);
            semerror(fs->ls, msg);
        }
    }
}


/* skip no-op statements */
static void skipnoopstat(LexState *ls)
{
    while (ls->t.token == ';' || ls->t.token == TK_DBCOLON)
        statement(ls);
}


static void labelstat(LexState *ls, TString *label, int line)
{
    /* label -> '::' NAME '::' */
    FuncState *fs = ls->fs;
    Labellist *ll = &ls->dyd->label;
    int l;  /* index of new label being created */
    checkrepeated(fs, ll, label);  /* check for repeated labels */
    checknext(ls, TK_DBCOLON);  /* skip double colon */
    /* create new entry for this label */
    l = newlabelentry(ls, ll, label, line, luaK_getlabel(fs));
    skipnoopstat(ls);  /* skip other no-op statements */
    if (block_follow(ls, 0))    /* label is last no-op statement in the block? */
    {
        /* assume that locals are already out of scope */
        ll->arr[l].nactvar = fs->bl->nactvar;
    }
    findgotos(ls, &ll->arr[l]);
}


static void whilestat(LexState *ls, int line)
{
    /* whilestat -> WHILE cond DO block END */
    FuncState *fs = ls->fs;
    int whileinit;
    int condexit;
    BlockCnt bl;
    luaX_next(ls);  /* skip WHILE */
    whileinit = luaK_getlabel(fs);
    condexit = cond(ls);
    enterblock(fs, &bl, 1);
    checknext(ls, TK_DO);
    block(ls);
    luaK_jumpto(fs, whileinit);
    check_match(ls, TK_END, TK_WHILE, line);
    leaveblock(fs);
    luaK_patchtohere(fs, condexit);  /* false conditions finish the loop */
}


static void repeatstat(LexState *ls, int line)
{
    /* repeatstat -> REPEAT block UNTIL cond */
    int condexit;
    FuncState *fs = ls->fs;
    int repeat_init = luaK_getlabel(fs);
    BlockCnt bl1, bl2;
    enterblock(fs, &bl1, 1);  /* loop block */
    enterblock(fs, &bl2, 0);  /* scope block */
    luaX_next(ls);  /* skip REPEAT */
    statlist(ls);
    check_match(ls, TK_UNTIL, TK_REPEAT, line);
    condexit = cond(ls);  /* read condition (inside scope block) */
    if (bl2.upval)  /* upvalues? */
        luaK_patchclose(fs, condexit, bl2.nactvar);
    leaveblock(fs);  /* finish scope */
    luaK_patchlist(fs, condexit, repeat_init);  /* close the loop */
    leaveblock(fs);  /* finish loop */
}


static int exp1(LexState *ls)
{
    expdesc e;
    int reg;
    expr(ls, &e);
    luaK_exp2nextreg(ls->fs, &e);
    lua_assert(e.k == VNONRELOC);
    reg = e.u.info;
    return reg;
}


static void forbody(LexState *ls, int base, int line, int nvars, int isnum)
{
    /* forbody -> DO block */
    BlockCnt bl;
    FuncState *fs = ls->fs;
    int prep, endfor;
    adjustlocalvars(ls, 3);  /* control variables */
    checknext(ls, TK_DO);
    prep = isnum ? luaK_codeAsBx(fs, OP_FORPREP, base, NO_JUMP) : luaK_jump(fs);
    enterblock(fs, &bl, 0);  /* scope for declared variables */
    adjustlocalvars(ls, nvars);
    luaK_reserveregs(fs, nvars);
    block(ls);
    leaveblock(fs);  /* end of scope for declared variables */
    luaK_patchtohere(fs, prep);
    if (isnum)  /* numeric for? */
        endfor = luaK_codeAsBx(fs, OP_FORLOOP, base, NO_JUMP);
    else    /* generic for */
    {
        luaK_codeABC(fs, OP_TFORCALL, base, 0, nvars);
        luaK_fixline(fs, line);
        endfor = luaK_codeAsBx(fs, OP_TFORLOOP, base + 2, NO_JUMP);
    }
    luaK_patchlist(fs, endfor, prep + 1);
    luaK_fixline(fs, line);
}


static void fornum(LexState *ls, TString *varname, int line)
{
    /* fornum -> NAME = exp1,exp1[,exp1] forbody */
    FuncState *fs = ls->fs;
    int base = fs->freereg;
    new_localvarliteral(ls, "(for index)");
    new_localvarliteral(ls, "(for limit)");
    new_localvarliteral(ls, "(for step)");
    new_localvar(ls, varname);
    checknext(ls, '=');
    exp1(ls);  /* initial value */
    checknext(ls, ',');
    exp1(ls);  /* limit */
    if (testnext(ls, ','))
        exp1(ls);  /* optional step */
    else    /* default step = 1 */
    {
        luaK_codek(fs, fs->freereg, luaK_intK(fs, 1));
        luaK_reserveregs(fs, 1);
    }
    forbody(ls, base, line, 1, 1);
}


static void forlist(LexState *ls, TString *indexname)
{
    /* forlist -> NAME {,NAME} IN explist forbody */
    FuncState *fs = ls->fs;
    expdesc e;
    int nvars = 4;  /* gen, state, control, plus at least one declared var */
    int line;
    int base = fs->freereg;
    /* create control variables */
    new_localvarliteral(ls, "(for generator)");
    new_localvarliteral(ls, "(for state)");
    new_localvarliteral(ls, "(for control)");
    /* create declared variables */
    new_localvar(ls, indexname);
    while (testnext(ls, ','))
    {
        new_localvar(ls, str_checkname(ls));
        nvars++;
    }
    checknext(ls, TK_IN);
    line = ls->linenumber;
    adjust_assign(ls, 3, explist(ls, &e), &e);
    luaK_checkstack(fs, 3);  /* extra space to call generator */
    forbody(ls, base, line, nvars - 3, 0);
}


static void forstat(LexState *ls, int line)
{
    /* forstat -> FOR (fornum | forlist) END */
    FuncState *fs = ls->fs;
    TString *varname;
    BlockCnt bl;
    enterblock(fs, &bl, 1);  /* scope for loop and control variables */
    luaX_next(ls);  /* skip 'for' */
    varname = str_checkname(ls);  /* first variable name */
    switch (ls->t.token)
    {
    case '=':
        fornum(ls, varname, line);
        break;
    case ',':
    case TK_IN:
        forlist(ls, varname);
        break;
    default:
        luaX_syntaxerror(ls, "'=' or 'in' expected");
    }
    check_match(ls, TK_END, TK_FOR, line);
    leaveblock(fs);  /* loop scope ('break' jumps to this point) */
}


static void test_then_block(LexState *ls, int *escapelist)
{
    /* test_then_block -> [IF | ELSEIF] cond THEN block */
    BlockCnt bl;
    FuncState *fs = ls->fs;
    expdesc v;
    int jf;  /* instruction to skip 'then' code (if condition is false) */
    luaX_next(ls);  /* skip IF or ELSEIF */
    expr(ls, &v);  /* read condition */
    checknext(ls, TK_THEN);
    if (ls->t.token == TK_GOTO || ls->t.token == TK_BREAK)
    {
        luaK_goiffalse(ls->fs, &v);  /* will jump to label if condition is true */
        enterblock(fs, &bl, 0);  /* must enter block before 'goto' */
        gotostat(ls, v.t);  /* handle goto/break */
        skipnoopstat(ls);  /* skip other no-op statements */
        if (block_follow(ls, 0))    /* 'goto' is the entire block? */
        {
            leaveblock(fs);
            return;  /* and that is it */
        }
        else  /* must skip over 'then' part if condition is false */
            jf = luaK_jump(fs);
    }
    else    /* regular case (not goto/break) */
    {
        luaK_goiftrue(ls->fs, &v);  /* skip over block if condition is false */
        enterblock(fs, &bl, 0);
        jf = v.f;
    }
    statlist(ls);  /* 'then' part */
    leaveblock(fs);
    if (ls->t.token == TK_ELSE ||
            ls->t.token == TK_ELSEIF)  /* followed by 'else'/'elseif'? */
        luaK_concat(fs, escapelist, luaK_jump(fs));  /* must jump over it */
    luaK_patchtohere(fs, jf);
}


static void ifstat(LexState *ls, int line)
{
    /* ifstat -> IF cond THEN block {ELSEIF cond THEN block} [ELSE block] END */
    FuncState *fs = ls->fs;
    int escapelist = NO_JUMP;  /* exit list for finished parts */
    test_then_block(ls, &escapelist);  /* IF cond THEN block */
    while (ls->t.token == TK_ELSEIF)
        test_then_block(ls, &escapelist);  /* ELSEIF cond THEN block */
    if (testnext(ls, TK_ELSE))
        block(ls);  /* 'else' part */
    check_match(ls, TK_END, TK_IF, line);
    luaK_patchtohere(fs, escapelist);  /* patch escape list to 'if' end */
}


static void localfunc(LexState *ls)
{
    expdesc b;
    FuncState *fs = ls->fs;
    new_localvar(ls, str_checkname(ls));  /* new local variable */
    adjustlocalvars(ls, 1);  /* enter its scope */
    body(ls, &b, 0, ls->linenumber);  /* function created in next register */
    /* debug information will only see the variable after this point! */
    getlocvar(fs, b.u.info)->startpc = fs->pc;
}


static void localstat(LexState *ls)
{
    /* stat -> LOCAL NAME {',' NAME} ['=' explist] */
    int nvars = 0;
    int nexps;
    expdesc e;
    do
    {
        new_localvar(ls, str_checkname(ls));
        nvars++;
    }
    while (testnext(ls, ','));
    if (testnext(ls, '='))
        nexps = explist(ls, &e);
    else
    {
        e.k = VVOID;
        nexps = 0;
    }
    adjust_assign(ls, nvars, nexps, &e);
    adjustlocalvars(ls, nvars);
}


static int funcname(LexState *ls, expdesc *v)
{
    /* funcname -> NAME {fieldsel} [':' NAME] */
    int ismethod = 0;
    singlevar(ls, v);
    while (ls->t.token == '.')
        fieldsel(ls, v);
    if (ls->t.token == ':')
    {
        ismethod = 1;
        fieldsel(ls, v);
    }
    return ismethod;
}


static void funcstat(LexState *ls, int line)
{
    /* funcstat -> FUNCTION funcname body */
    int ismethod;
    expdesc v, b;
    luaX_next(ls);  /* skip FUNCTION */
    ismethod = funcname(ls, &v);
    body(ls, &b, ismethod, line);
    luaK_storevar(ls->fs, &v, &b);
    luaK_fixline(ls->fs, line);  /* definition "happens" in the first line */
}


static void exprstat(LexState *ls)
{
    /* stat -> func | assignment */
    FuncState *fs = ls->fs;
    struct LHS_assign v;
    suffixedexp(ls, &v.v);
    if (ls->t.token == '=' || ls->t.token == ',')   /* stat -> assignment ? */
    {
        v.prev = NULL;
        assignment(ls, &v, 1);
    }
    else    /* stat -> func */
    {
        check_condition(ls, v.v.k == VCALL, "syntax error");
        SETARG_C(getinstruction(fs, &v.v), 1);  /* call statement uses no results */
    }
}


static void retstat(LexState *ls)
{
    /* stat -> RETURN [explist] [';'] */
    FuncState *fs = ls->fs;
    expdesc e;
    int first, nret;  /* registers with returned values */
    if (block_follow(ls, 1) || ls->t.token == ';')
        first = nret = 0;  /* return no values */
    else
    {
        nret = explist(ls, &e);  /* optional return values */
        if (hasmultret(e.k))
        {
            luaK_setmultret(fs, &e);
            if (e.k == VCALL && nret == 1)    /* tail call? */
            {
                SET_OPCODE(getinstruction(fs, &e), OP_TAILCALL);
                lua_assert(GETARG_A(getinstruction(fs, &e)) == fs->nactvar);
            }
            first = fs->nactvar;
            nret = LUA_MULTRET;  /* return all values */
        }
        else
        {
            if (nret == 1)  /* only one single value? */
                first = luaK_exp2anyreg(fs, &e);
            else
            {
                luaK_exp2nextreg(fs, &e);  /* values must go to the stack */
                first = fs->nactvar;  /* return all active values */
                lua_assert(nret == fs->freereg - first);
            }
        }
    }
    luaK_ret(fs, first, nret);
    testnext(ls, ';');  /* skip optional semicolon */
}


static void statement(LexState *ls)
{
    int line = ls->linenumber;  /* may be needed for error messages */
    enterlevel(ls);
    switch (ls->t.token)
    {
    case ';':    /* stat -> ';' (empty statement) */
    {
        luaX_next(ls);  /* skip ';' */
        break;
    }
    case TK_IF:    /* stat -> ifstat */
    {
        ifstat(ls, line);
        break;
    }
    case TK_WHILE:    /* stat -> whilestat */
    {
        whilestat(ls, line);
        break;
    }
    case TK_DO:    /* stat -> DO block END */
    {
        luaX_next(ls);  /* skip DO */
        block(ls);
        check_match(ls, TK_END, TK_DO, line);
        break;
    }
    case TK_FOR:    /* stat -> forstat */
    {
        forstat(ls, line);
        break;
    }
    case TK_REPEAT:    /* stat -> repeatstat */
    {
        repeatstat(ls, line);
        break;
    }
    case TK_FUNCTION:    /* stat -> funcstat */
    {
        funcstat(ls, line);
        break;
    }
    case TK_LOCAL:    /* stat -> localstat */
    {
        luaX_next(ls);  /* skip LOCAL */
        if (testnext(ls, TK_FUNCTION))  /* local function? */
            localfunc(ls);
        else
            localstat(ls);
        break;
    }
    case TK_DBCOLON:    /* stat -> label */
    {
        luaX_next(ls);  /* skip double colon */
        labelstat(ls, str_checkname(ls), line);
        break;
    }
    case TK_RETURN:    /* stat -> retstat */
    {
        luaX_next(ls);  /* skip RETURN */
        retstat(ls);
        break;
    }
    case TK_BREAK:   /* stat -> breakstat */
    case TK_GOTO:    /* stat -> 'goto' NAME */
    {
        gotostat(ls, luaK_jump(ls->fs));
        break;
    }
    default:    /* stat -> func | assignment */
    {
        exprstat(ls);
        break;
    }
    }
    lua_assert(ls->fs->f->maxstacksize >= ls->fs->freereg &&
               ls->fs->freereg >= ls->fs->nactvar);
    ls->fs->freereg = ls->fs->nactvar;  /* free registers */
    leavelevel(ls);
}

/* }====================================================================== */


/*
** compiles the main function, which is a regular vararg function with an
** upvalue named LUA_ENV
*/
static void mainfunc(LexState *ls, FuncState *fs)
{
    BlockCnt bl;
    expdesc v;
    open_func(ls, fs, &bl);
    fs->f->is_vararg = 1;  /* main function is always declared vararg */
    init_exp(&v, VLOCAL, 0);  /* create and... */
    newupvalue(fs, ls->envn, &v);  /* ...set environment upvalue */
    luaX_next(ls);  /* read first token */
    statlist(ls);  /* parse main body */
    check(ls, TK_EOS);
    close_func(ls);
}


LClosure *luaY_parser(lua_State *L, ZIO *z, Mbuffer *buff,
                      Dyndata *dyd, const char *name, int firstchar)
{
    LexState lexstate;
    FuncState funcstate;
    LClosure *cl = luaF_newLclosure(L, 1);  /* create main closure */
    setclLvalue(L, L->top, cl);  /* anchor it (to avoid being collected) */
    luaD_inctop(L);
    lexstate.h = luaH_new(L);  /* create table for scanner */
    sethvalue(L, L->top, lexstate.h);  /* anchor it */
    luaD_inctop(L);
    funcstate.f = cl->p = luaF_newproto(L);
    funcstate.f->source = luaS_new(L, name);  /* create and anchor TString */
    lua_assert(iswhite(funcstate.f));  /* do not need barrier here */
    lexstate.buff = buff;
    lexstate.dyd = dyd;
    dyd->actvar.n = dyd->gt.n = dyd->label.n = 0;
    luaX_setinput(L, &lexstate, z, funcstate.f->source, firstchar);
    mainfunc(&lexstate, &funcstate);
    lua_assert(!funcstate.prev && funcstate.nups == 1 && !lexstate.fs);
    /* all scopes should be correctly finished */
    lua_assert(dyd->actvar.n == 0 && dyd->gt.n == 0 && dyd->label.n == 0);
    L->top--;  /* remove scanner's table */
    return cl;  /* closure is on the stack, too */
}

